Just because General Motors calls it green doesn’t mean it is.

Joel Makower reports that General Motors will lead a joint demonstration project "to learn more about consumer awareness and acceptance of E85 as a motor vehicle fuel by demonstrating its use in GM’s flexible-fuel vehicles."

The California Department of Transportation will use some flex-fuel vehicles and work with Chevron Technology Ventures to make sure there are filling stations that offer E85 (gas w/ 85% ethanol). A company called Pacific Ethanol will provide the liquid fuel. Filling stations that sell E85 will be receiving "a lucrative federal tax credit."

Joel passes rather lightly over the central problem with biofuels, a problem advocates have never satisfactorily resolved. We’re always told that biomass for ethanol could come from crop waste, fryer grease, turkeys, or what have you, but what it inevitably will be made from is whatever’s cheapest.

Right now it’s cheapest to use corn, sugarcane, soybeans, and palm oil — heavily-subsidized agribusiness products. Joel holds Brazil up as a model, boasting that it just became a net exporter of sugarcane ethanol. But right there in Brazil rainforests are being plowed down to plant crops, making carbon sinks into carbon sieves.

If there were more confident predictions and fewer just-so stories about how genuinely renewable sources of ethanol will become cheaper than biodiversity-destroying, CO2-increasing agricultural crops, I would feel more comfortable biofuel boosting.

I’m not ready to walk blindly into this future, holding General Motors’ hand for comfort.